Arranging a dependency tree

[Kyle Root]

I'm working on a little practice program, but I've become stuck and am
now utterly confused :?

I've created a jumble of python modules, in each one is a tuple that
goes something like,

deps = ("file10","file7","file3").

And some have no dependencies at all.  I have one file called "start",
and the whole thing makes a tree of dependencies as each file has deps
and their deps might have deps, and so on.  What I'm trying to do is
"straighten" them or put them in order as if they were to be
installed.  Basically I'm trying to replicate the way portage does it.
:)

I've been thinking about this for a few days but I always get lost. 
So far I have a has_deps(filename) function, and not much else. I get
stuck on the actual changing the files from the random jumble to a
into a nice orderly list of files.    One problem that I can't
overcome is when I'm a couple of deps in and I finally get to the
files that don't require anything, I have no way of getting back to do
the parent file's other deps. (Does that make any sense?)

Basically I was wondering if anyone had any tips or pointers, or knew
of any dependency resolving algorithms...

Thanks,
Kyle